1. Field of the Invention
The present invention relates to a disk device including a plurality of recording surfaces that has a recording area for recording data, a disk formatting method, and a disk formatting apparatus, and more particularly, to a disk device that can use an appropriate area as an effective area for recording the data according to head positioning accuracies that are different between respective heads and improve a recording quality, a disk formatting method, and a disk formatting apparatus.
2. Description of the Related Art
A recording density of a hard disk drive (HDD) is improved year by year to increase a recording capacity of the HDD. To improve the recording density, a further reduction in the width of a track on which data is recorded and a further reduction in flying height of heads used for writing and readout of the data are demanded. Therefore, in recent years, a head positioning accuracy is getting more and more susceptible to an influence of very small distortion of a disk surface.
FIG. 7 is a side sectional view of a structure of a support member in the center of a disk surface. As shown in the figure, a disk device has two disks, an upper disk 301 and a lower disk 302. The lower disk 302 is supported by a spacer 312 and a spindle motor (SPM) hub 313, both of which are planar components. On the other hand, the upper surface of the upper disk 301 is supported by a disk clamp 311, which is a component having a curved surface. Therefore, very small distortion tends to occur in the upper surface of the upper disk 301 compared with the lower disk 302. Very small distortion also tends to occur in the lower surface of the upper disk 301 on the opposite side of the upper surface because of the influence of the disk clamp 311.
In a conventional HDD, an innermost area position, which is a boundary on the inner side of a disk use area used for data recording, is set in a position offset to the outer side by a fixed amount from an inner side stopper position, which is a limit position that the heads can seek. When the innermost area position is determined based on an actuator stroke in this way, the innermost area position is basically a position identical for all the heads.
FIG. 8 is a diagram for explaining a difference of head positioning accuracies between heads. As shown in the figure, in the disk device having the two disks, because of the difference of the spaces of the members that support the respective disk surfaces shown in FIG. 7, a head positioning accuracy in the upper disk 301 is low compared with that in the lower disk 302. The difference is more marked further on the inner side of the disks. Therefore, in the conventional method of determining an innermost area position based on an actuator stroke, a head positioning accuracy near the innermost area position of the upper disk is excessively deteriorated to cause deterioration in a recording quality.
A disk formatting method of dividing a disk use area into a plurality of zones and setting different track pitches (data recording densities in a disk radial direction) or readout/writing frequencies (data recording densities in a disk circumferential direction) in the respective zones divided is disclosed (see, for example, Japanese Patent Application Laid-Open No. H8-255412).
However, in the disk formatting method according to the conventional technology, an innermost area position is identical on an upper disk and a lower disk. Thus, when a head positioning accuracy is excessively deteriorated, a portion near the innermost area position of the upper disk is also included in the disk use area.